This study proposes to apply the extensive knowledge of the Dorsal gradient in Drosophila to understand evolutionary changes in the gastrulation of the honeybee, Apis mellifera. In Drosophila, the ventral-most cells invaginate into the blastocoel and then spread along the internal surface of the neurogenic ectoderm. In contrast, Apis embryos exhibit a classical "epiboly", where ventral ectoderm spreads over the ventral mesoderm. A major goal of the following research plan is to describe this difference in gastrulation movements in terms of changes in the cis-regulation of genes downstream of the Dorsal gradient. To identify such potential changes, precise knowledge of the relative expression of "gastrulation RNAs" in Drosophila and the Apis homologues will be determined using simultaneous confocal imaging of multiple RNAs in embryos. This will inform bioinformatic identification of orthologous, but functionally divergent, enhancers from the nearly completed Apis genome. The function of these enhancers will then be assayed in transgenic Drosophila and Apis embryos. It is our hope that this will lead to a specific understanding of the evolution of transcriptional regulation and to events that underlie transition of cells toward a migratory state.